1. Field of the Invention
The present invention is directed to vehicles for transporting a payload and, more particularly, to a multicombination vehicle for transporting a payload, such as a mined ore, over the roadways in an underground mine. The multicombination vehicle includes at least one powered, load-carrying towing unit and at least one load-carrying towed unit. The multicombination vehicle is configured to minimize the swept path width of the vehicle to permit operation within the relatively narrow tunnels and included relatively low radius turns typically found in underground mines.
2. Related Art
Mined payloads, such as various metal ores, are typically transported through the tunnels of an underground mine by either a railway train including a locomotive and one or more cars operating on a fixed system of railway tracks, or rigid body, load-carrying trucks. Although each known system may be advantageously utilized in certain applications, they are both subject to various disadvantages.
An underground railway system is relatively expensive to install and operate due to the cost of acquiring the locomotive and installing the fixed railway system and the associated maintenance costs. Furthermore, and perhaps more importantly, an underground railway system is route-specific and therefore not flexible to changes in route without incurring the expense of installing additional railway tracks. Underground mines typically have several mining areas, which may occur on multiple levels within the mine. The mined product, such as ore, is typically transported from each mining area to a common receiving area, and then through one or more vertical chutes connecting different levels of the mine if required, to a central processing area where the ore is processed, or sufficiently crushed. The ore is then typically removed from the mine through a single vertical shaft extending to the surface. A single ore crusher and associated shaft is typically used due to the prohibitive costs associated with drilling a shaft from the surface to the mining area deep below the ground. As each new mining area opens, it is necessary to incur the cost of installing new track for the railway system, or to use supplemental vehicles to haul the ore from the mining area to the end of the railway track system.
Rigid body load-carrying trucks, such as wheeled dump trucks, are not route-specific since they are capable of traveling over various roadways within the mine between various origination and destination points. However, known trucks of this type are typically designed for hauling loads over relatively short distances and rough terrain, such as that which may be experienced in above-ground applications. Accordingly, such trucks are typically designed with relatively large tires for relatively slow speed operation and are relatively expensive to operate and maintain due to fuel and tire costs. The efficiency of these vehicles typically decreases as the hauling distance increases. Furthermore, a single rigid body truck of this type has a significantly lower payload capacity as compared to the multicombination vehicle of the present invention.
Multicombination vehicles commonly referred to as xe2x80x9croad trainsxe2x80x9d have been in use for some time, particularly in Australia, for the purpose of hauling mined products, or the commodities of other industries, over above-ground roadways. Known xe2x80x9croad trainsxe2x80x9d typically include a powered load-carrying towing vehicle such as a wheeled, rigid body truck and one or more load-carrying towed vehicles. The towed vehicles may include a wheeled dolly and a semi-trailer coupled to the dolly. Both the towing and towed vehicles may include load-carrying bodies of the side-tipping type. However, conventional xe2x80x9croad trainsxe2x80x9d are typically designed for use at relatively high speed, for instance at speeds up to 55-60 mph, and are therefore not capable of operating in an underground mine for the following reasons. Due to the relatively high speed, straight-down-the-road application of known above ground road trains, the mechanical coupling between each adjacent pair of vehicles is located as far forward as possible, or as close to the rear suspension of the upstream or forward vehicle, within the physical constraints imposed in a turning situation by the tow bar connecting the vehicles (i.e., to avoid contact between the tow bar and the chassis of the forward vehicle when turning). This location of mechanical couplings between each adjacent pair of vehicles is required to maintain the side-to-side sway, or yaw, of the last vehicle within acceptable limits for aboveground, over-the-road application, but is not compatible for operation within an underground mine due to the relatively low operating speeds as well as the relatively narrow tunnels and small radius bends experienced in underground mines. The inventor is unaware of any known above ground, road-legal multicombination vehicle of the type just described, which is capable of gaining access to an underground mine and operating within the profiles of the mine as typically exists in underground mines throughout the world.
In view of the foregoing disadvantages and limitations associated with known load-carrying vehicles, a commercial need exists for an improved load-carrying vehicle for use in underground mines.
Accordingly, the present invention provides a multicombination vehicle and method for transporting a payload, such as a mined metal ore, over the roadways existing in an underground mine. The multicombination vehicle has a significantly reduced swept path width as compared to conventional aboveground road trains which permits the multicombination vehicle of the present invention to gain access to and operate within the tunnels typically found in underground mines, such as those used to mine a metal ore. The multicombination vehicle of the present invention is not route-specific and therefore, is much more flexible than the use of an underground railway system to transport a payload within the underground mine. Furthermore, the use of the multicombination vehicle of the present invention has significantly higher payload-to-tare weight and payload-to-horsepower ratios than conventional dump trucks typically used to haul ore within an underground mine. This may result in a significant cost savings to the operator of the mine.
According to one embodiment of the present invention, the multicombination vehicle comprises a powered towing unit having a chassis, a forward, wheeled axle suspended from the chassis and a rear, wheeled axle assembly suspended from the chassis by a rear suspension system. The forward, wheeled axle and rear, wheeled axle assembly support the powered towing unit for movement over the roadway. The powered towing unit further includes a source of motive power, which may comprise a diesel engine or an electric motor, for instance, and means for transmitting torque from the source of motive power to the driving axle.
The multicombination vehicle further includes a towed unit mechanically coupled to the powered towing unit. The towed unit includes a chassis and a load-carrying body mounted on and disposed above the chassis. The towed unit further includes at least one wheeled, driven axle supporting the towed unit for movement over the roadways. The towed unit may include a forward, wheeled, tandem axle assembly suspended from the chassis by a first suspension system and a rear, wheeled, tandem axle assembly suspended from the chassis by a second suspension system. The towed unit has a wheelbase which is defined as the longitudinal distance between the longitudinal centers of the first and second suspension systems. The towed unit further includes a drawbar attached to and extending from the chassis of the towed unit.
The powered towing unit further includes a draw frame attached to and extending rearwardly from the chassis of the towing unit and a coupling attached to a rear end of the draw frame and connected with the drawbar of the towed unit. The powered towing unit has a wheelbase extending between the longitudinal centers of suspension of the forward axle and rear axle assembly. The powered towing unit further includes a coupling overhang defined as the longitudinal distance between a substantially vertical axis of rotation passing through the coupling and the longitudinal center of suspension of the rear axle assembly. The powered towing unit further includes a ratio of the coupling overhang to the wheelbase having a value of at least 0.5.
The towed unit preferably comprises a converter dolly and a semi-trailer having a forward end mounted on the converter dolly. Both the dolly and semi-trailer include a wheeled, tandem axle assembly. Each of the tandem axle assemblies includes a pair of wheeled, driven axles. The converter dolly further includes a chassis, a ball-race turntable mounted on an upper surface of the chassis and the drawbar of the towed unit, which may comprise an A-frame drawbar. The towed unit further comprises a dolly drawbar length defined as the longitudinal distance between a substantially vertical axis of rotation passing through the coupling which interconnects the powered towing unit and the towed unit, and the longitudinal center of a suspension system used to suspend the tandem axle assembly of the dolly. In a preferred embodiment, the dolly drawbar length has a value less than 3.0 m.
The powered towing unit further includes a load-carrying body mounted on and disposed above the chassis of the towing unit. The load-carrying bodies of the towing and towed units preferably comprise side-tipping, load-carrying bodies which may be actuated to a tipped position by a pair of actuators disposed proximate each of the opposing end portions of the corresponding load-carrying body.
In another preferred embodiment, the multicombination vehicle includes a plurality of the towed units, wherein a forward most one of the towed units is mechanically coupled to the powered towing unit and each adjacent pair of the towed units are mechanically coupled to one another. In this embodiment, each of the towed units has a dolly drawbar length having a value less than 3.0 meters and a coupling overhang-to-wheelbase ratio of at least 0.50. Furthermore, the load-carrying body of each of the towed units is a side-tipping, load-carrying body.
According to a second aspect of the present invention, a method is provided for transporting a mined payload over the roadways existing in an underground mine. According to a preferred embodiment, the method comprises the steps of providing a multicombination vehicle having a powered towing unit and at least one towed unit, with each adjacent pair of units being mechanically coupled to one another, and each of the units including a load-carrying body. The method further includes the steps of minimizing a swept path width of the multicombination vehicle as the vehicle travels over the roadways of the underground mine, loading pre-determined quantities of the payload into the load-carrying bodies of each of the units of the vehicle, driving the vehicle over at least one of the roadways to a payload-dumping area, and dumping the payload from the load-carrying bodies of each of the units into a receptacle disposed in the payload-dumping area.
The step of minimizing the swept path width may include the steps of establishing a ratio of the coupling overhang to the wheelbase of at least 0.5, for each unit of the vehicle, and configuring each of the towed units so that the dolly drawbar length of each of the towed units has a value less than 3.0 meters.
According to other embodiments, the loading step may further comprise the steps of driving the multicombination vehicle over at least one of the roadways to a payload-receiving area on a first one of the mine levels, positioning the load-carrying body of one of the units of the vehicle under an overhead hopper disposed above the roadway of the first mine level and depositing a pre-determined quantity of the payload into the overhead hopper from a second level of the mine disposed above the first level. The loading step further includes the step of dumping the pre-determined quantity of the payload into the load-carrying body and repeating the steps of positioning, depositing and dumping as required to substantially fill the load-carrying bodies of each of the units of the multicombination vehicle.